Track fullness system



Nov. 3, 1964 R. D. CAMPBELL TRACK FULLNESS SYSTEM 3 Sheets-Sheet 1 Filed June 5, 1962 MEN mmk

INVENTOR. Richard 17. dazzzpbel Nov. 3, 1964 R. D. CAMPBELL TRACK FULLNESS SYSTEM 3 Sheets-Sheet 2 Filed June 5, 1962 R. D. CAMPBELL TRACK FULLNESS SYSTEM Nov. 3, 1964 3 Sheets-Sheet 3 Filed June 5, 1962 Talc/i Fall Track Fmpy INVENTOR. z'cbafld D. Canzpbell.

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H15 ATTORNEY United States Patent 3,155,350 TRACK FULLNESS SYTEM Richard D. Campbell, Harmarville, Pa, assignor to Westinghouse Air Brake Company, Wilmer-ding, Pa, a corporation of Pennsylvania Filed June 5, 1962, Ser. No. 209,207 12 Claims. (Cl. 246-412) My invention relates to a track fullness system, and more particularly to a system for determining and indicating the distance cars being classified in a railway car classification yard of the gravity type have to travel in a storage track to couple with the last car previously routed to such track.

In the most modern railway car classification systems, railway yards of the gravity or hump type are employed and the railway cars to be classified are moved over the crest of the hump by a switching locomotive and thereafter proceed to their respective classification or storage tracks in the yard under the influence of gravity. In order that the cars will travel to coupling with the preceding cars in their respective storage tracks but will not couple with an excessive impact, track brakes or car retarders are provided in each route to provide the correct retardation for each cut of one or more cars traversing the retarders and thereby provide the desired operation.

Among the various factors to be considered in determining the correct leaving speed of a cut from a retarder, in order that it will travel to coupling without excessive impact with preceding cars, is the number of cars already in the destined storage track for the cut or, more correctly stated, the distance for the cut to travel to coupling. Many of the track fullness systems heretofore employed in railway car classification yards make use of car counting or axle counting devices to determine the number of cars that have been routed to each track and, thereby, provide a measurement of the fullness of each individual track. However, the number of cars routed to each particular storage track is not always indicative of the distance to travel to coupling with preceding cars in a storage track since a previous car out routed to that track could have stopped short of its destination and thereby have reduced the distance to travel to coupling for the next car cut to be routed to that track.

It has heretofore been proposed to provide an alternating current track circuit in each storage track in a classification yard and to measure the impedance of each such track circuit to determine the distance between the entering end of the respective storage track and the nearest track circuit shunt, that is, to the nearest pair of railway car wheels and associated axle. Such a system employs the value of voltage across the rails, at the points of connection thereto of the alternating current, as a measurement of the impedance of the rails between such points of connection and the nearest pair of railway car wheels and'axle. Such voltage varies approximately as the distance between said points of connection and said car wheels.

It has been found in such alternating current track circuit organizations that the shift in phase angle of the alternating current supplied to the track, such shift occuring due to the variations in impedance of the rails of the track occasioned by varying distances to the nearest shunt across such rails, provides a truer and more reliable measurement of the distance to travel to coupling in such track. Accordingly, it is one object of my invention to provide a track fullness system in which the degree of phase angle displacement of an alternating current supplied across the rails of astorage track in a classification yard is the criterion employed to determine the distance to travel to coupling in such track.

Patented Nov. 3, 1964 It is another object of my invention to provide a track fullness or distance to travel system that takes into account cars of unusual length and cars that stop short of cou pling in a storage track.

It is a third object of my invention to provide a track fullness system that is self-adjusting following the removal of cars from a storage track.

It is a further object of my invention to provide new and novel means for detecting cars moving in a storage track during a measurement of the distance to travel to coupling in the storage track and, if moving cars are detected, to invalidate such measurement.

In accomplishing the foregoing objects of my invention I employ alternating current phase angle displacement detection means for measuring the distance to travel in a storage track and for detecting movement of a car or cars in such storage track. I also provide means for invalidation of the track fullness information if car movement in the storage track is detected.

Other objects and characteristic features of my invention will become apparent as the description proceeds.

I shall first describe one embodiment of my invention and shall then point out the novel features thereof in claims.

In the accompanying drawings FIGS. 1 and 1a when arranged as shown in FIG. 1b comprise a diagrammatic view of track fullness or distance to travel apparatus embodying my invention.

FIG. 2 comprises a timing diagram employed to aid in an understanding of the operation of the track fullness system of my invention.

There is shown in FIG. 1 a motor-generator set designated MG and having its motor M connected across the terminals of a commercial source of alternating current. For purposes of simplicity such source of current is not shown in the drawings but its terminals are designated BX and NX. The motor-generator set is intended to function as a filter to provide 60 c.p.s. power, as an example, which is free of power line voltage fluctuation. Such voltage fluctuation free power is unnecessary so far as the track fullness measuring apparatus of my invention is concerned, but is required for the motion detection apparatus of my invention hereinafter discussed. Of course, if another source of alternating current which is free of power line voltage fluctuations is available, the motor-generator set is not required.

The output terminals of generator G of the motor-generator set MG are connected to the winding of an autotransformer TF1 so that a generator output of v. will provide at the end terminals of the winding of transformer TF1 an output of approximately v., for example. One of the end terminals of transformer TF1 is connected to ground and the other terminal is connected through a 350 ohm resistor REL for example, to one end of the primary windings of each of second and third transformers designated TF2 and TF3 respectively. The second end of the primary winding of the transformer TF2 is connected to a tap on the winding of autotransformer TF1 at approximately the 75% point of the winding. The second end of the primary winding of transformer TF3 is connected to ground. Transformer TF3 is a step-down transformer having approximately a 30 to 1 ratio and transformer TF2 is a step-up transformer having approximately a 1 to 5 ratio.

It is to be understood at the outset that the apparatus organization per se, described above, forms no part of my invention and that the given voltage and resistor values, and the transformer ratios could be other than those stated. Furthermore other alternating current track circuit apparatus organizations could conceivably be employed. The track circuit apparatus shown and discussed to this point, and the values and ratios stated are merely given as one example of such apparatus that has been found to operate very successfully with the apparatus of my invention. Further discussion and the operation of the above described apparatus will be set forth later in the specification.

There is also shown in FIG. 1 a section of railway track designated IT and intended to illustrate a railway car storage track in a gravity type railway car classification yard. Railway cars routed to the storage track enter the track from the left hand end thereof and proceed by gravity to the right hand end of the track or to coupling with previous cars routed to such track. The rails of storage track 1T are insulated from the rails of the track section to the left and right thereof by insulated rail joints 1, shown in the drawings by short lines drawn perpendicularly across the rails. The storage track is provided with an alternating current track circuit or loop circuit in cluding the secondary winding of previously discussed track transformer TF3, connected through a resistor REE across the rails of the storage track at the entering end thereof, and a conductor CN connected across the rails of the storage track at the end thereof remote from the transformer. This loop circuit for storage track 1T thus extends from one side of the secondary winding of transformer TF3 through resistor RE2, one of the rails of the storage track, conductor CN, and the other rail of the storage track to the other side of the secondary winding of transformer TF3. Resistor REZ is adjustable so that the alternating current loop track circuit can be readily adjusted for proper operation.

It is believed that a further brief discussion of the principles employed by my invention in determining track fullness and movement detection will be appropriate at this point in the description.

The impedance of a section of railway track to the flow of an alternating current supplied thereto is dependent upon its length, the size of the rails andthe condition of the ballast between the rails. Such impedance includes inductive and capacitive components of which the reactance parameter of the impedance of the track section is comprised and upon which phase angle displacement of the alternating current depends. For an example, it has been found in one installation, employed herein only as an example of the operation of the apparatus of my invention, that the impedance of a section of railway storage track having a length of 2700 feet has a reactive component which produces a phase angle displacement of approximately 72 degrees in a 60 c.p.s. alternating current supplied across the rails of the track section. Such track section has an electrical conductor or shunt, similar to conductor CN shown in FIG. 1 of applicants drawings, connected across the rails at a point 2700 feet from the points of connection of the alternating current supplied thereto. Since the length of an average railway car is considered to be 45 feet, 60 railway cars could be stored in the 2700 foot track section.

The shunt across the track rails caused by the rear Wheels and associated axle of each additional railway car routed to said storage track and traveling to coupling with the previous cars in 'suchtrack, in effect reduces the length of'the track circuit by 45 feet and causes a change of approximately 1.2 degrees in phase angle shift of the alternating current supplied to the track rails. In other words, if there are no cars in the storage track, a phase displacement of 72 degrees in the alternating current occurs and, if the track is full, that is, if the last pair of wheels and associated axle of the last car to enter the track are adjacent the points of connection ofthe alternating current supplied to the rails, substantially no phase displacement of the alternating current takes place. it isthus readily apparent that each car to enter the storage track and traveling to coupling with the previous cars routed to such track causes a reduction in phase angle displacement of 1.2 degrees; The phase angle displacement of the alternating current is, therefore, indicative of the distance to travel or track fullness of the storage track.

Referring again to FIG. 1 of applicants drawings, it will be seen that one end of the secondary winding of transformer TF2, previously discussed, is connected to ground and the output from the second end of such winding is supplied to a clipper circuit designated CL3. The impedance of track section or storage track 11 is reflected into the primary winding of transformer TF3 and in turn into the primary and secondary windings of transformer T F2, and the alternating current supplied to clipper circuit CL3 from the secondary winding of transformer TF2 reflects the phase shift occasioned by the impedance of track section 11'. In order to have a reference against which to compare the phase shifted alternating track circuit current and thereby determine, as hereinafter discussed, the degree of such phase shift, the point of the winding of autotransforrner TF1, in addition to being connected to the second end of the primary winding of transformer TF2, as previously mentioned, also supplies a reference alternating current to a clipper circuit designated CL]. and to a 72 degree phase shifter designated PS2.

The output of clipper circuit CLl is supplied to a degree phase shifter designated PS1 and the output of 72 degree phase shift PS2 is supplied to another clipper circuit designated CLZ. Clipper circuits CLl, CLZ and GL3 clip the alternating current sine waves supplied thereto to convert such waves into substantially square waveforms or pulses. The outputs of clipper circuits CLZ and GL3 are supplied to the grids of electron tubes designated ET2 and ET3, respectively. Similarly, the output of phase shifter PS1 is supplied to the grid of an electron tube designated ETI. These tubes are here shown as triodes and have their cathodes connected in multiple with each other and to the negative terminal of a source of direct current. Similarly, the plates of the tubes are connected in multiple with each other and through a resistor RE3 to the positive terminal of said source of direct current. For purposes of simplicity this direct current source is not shown in the drawings but its positive and negative terminals are designated by the conventional symbols and respectively. The plates of tubes ETl, ETZ and ET3 are connected to the input of an integrator designated INT hereinafter discussed. Clipper circuits, phase shifters and triode electron tubes are well known components, and no detailed discussion of such apparatus is believed necessary except as in the following discussion of the operation of the triode tubes and in conjunction with the diagram of FIG. 2.

Electron tubes ETl, ETZ and ET3 and their connections, discussed above, form a basic computer circuit employing AND logic which is in reality a NOR circuit in accordance with the Boolean algebraic equation A+B U=an output Referring to FIG. 1, it will be readily apparent that tube ETl is conducting only when a positive current pulse is supplied from phase shifter PS1 to the grid of the tube. Similarly, tubes ET2 and ET3 are conducting only when positive current pulses are supplied from clipper circuits CL2 and GL3 to the grids of tubes ET2 and ET3, respectively. When any one or more of the tubes are conducting the current from the positive terminal of the previously mentioned direct current source flows from the plates of the conducting tube or tubes to the cathodes of such tubes and thence to the negative terminal of such current source. No current is supplied to integrator INT at such time. When all three tubes are nonconducting or oif, that is, when no positive current pulses are supplied to the grids of any of the tubes, current from the positive terminal of the direct current source is supplied to integrator INT. The operation of the .track fullness apparatus thus far described will be readily understood from the following discussion of the diagram shown in FIG. 2 of applicants drawings.

Waveform A of FIG. 2 is intended to illustrate the pulses from the output of clipper circuit CLl (FIG. 1) such output pulses being in phase with the sine wave of the reference alternating current supplied to said clipper circuit from autotransformer TF1. Waveform B illustrates the pulses from the output of 180 degree phase shifter PS1, such pulses being supplied to the grid of electron tube ET1 (FIG. 1). It is readily apparent that these pulses are illustrated in FIG. 2 as being shifted in phase 180 degrees from the pulses illustrated in Waveform A.

Waveform C illustrates the pulses from the output of clipper circuit CLZ (FIG. 1), such pulses being supplied to the grid of electron tube ET2. These pulses are shown as shifted in phase 72 degrees from the pulses shown in waveform A, such phase shifting being provided by 72 degree phase shifter PS2.

Waveform D illustrates the output pulses from clipper circuit GL3 when the alternating current sine Wave from the secondary winding of transformer TF2 (FIG. 1) is shifted so that it leads the reference alternating current sine wave by 18 degrees. A leading phase shift may occur when the storage track is completely full and the track circuit apparatus is out of adjustment. However, the 18 degree leading phase shift is an exaggeration employed only for purposes of convenient illustration in the diagram of FIG. 2 and normally any change in the adjustment of the track circuit will result in an improper phase shift of only a few degrees. The waveform D shown in FIG. 2 is intended to illustrate that storage track IT is full when the sine Wave of the alternating current from the secondary Winding of transformer TF2 is shifted as shown in waveform D and, therefore, that no direct current pulses are supplied to integrator INT at such time. The normal pulse waveform from clipper circuit CL3, when the track circuit apparatus is in perfect adjustment and the track is full, is illustrated by waveform E, and waveform E illustrates that again no direct current pulses are supplied to integrator INT at such time.

Referring to waveforms B, C and D it will be readily apparent that at no time are all three waveforms simultaneously in the lower half of their cycles or in their off condition. This is also true about waveforms B, C and E. Consequently the grids of one or more of electron tubes ET1, ET2 and ET3 are being supplied with positive current under conditions of waveforms D and E and at least one of such tubes is, therefore, always in its on condition and conducting. Thus no direct current is supplied to integrator INT at such time since the current from the positive terminal of the direct current source flows through the conducting tube or tubes to the negative terminal of such source. As will become apparent hereinafter, the total lack of current to integrator INT results in a track full indication.

Referring to waveform F in FIG. 2 it will be seen that the pulses of such waveform lag in phase the reference pulses of waveform A by 18 degrees. As indicated in the drawing, waveform F is intended to provide an indication that track section or storage track IT is /4 full, that is, empty and that 15 average car spaces are available in the track (each car space or 45 feet of available space being represented 'by 1.2 degrees of phase shift). Referring to waveform F it will be seen that pulses having and 18 degree width result from waveform F-being supplied to the grid of electron tube ET3. Waveform F occurs due to waveforms B, C and F being simultaneously in the lower halfof their cycles or off for 18 degrees of their full cycles. During such periods no positive current is supplied to the grids of any of the tubes ET1, ET2 and ET3 and all three tubes are, there:

"fore, non-conducting. Current from the positive terminal (-1-) of the direct current source is, therefore, sup: plied to the integrator INT during said periodsp such current during said periods resulting in pulses of direct current represented by waveform F. Waveforms G and H represent the pulses supplied to the grid of tube ET3 when storage track IT is half full and completely empty, respectively. Waveforms G and H show the width of the pulses supplied to integrator INT in response to the pulses of waveforms G and H, respectively, that is 36 degree and 72 degree width pulses, respectively. In view of the above detailed discussion relative to the pulses of waveforms F and F, no detailed discussion of the NOR circuit including tubes ET1, ET2 and ET3, relative to waveforms G, G, H and H is believed necessary in view of the self-explanatory nature of the diagram of FIG. 2.

Referring to waveform I of FIG. 2 it will be seen that a phase shift of degrees in the pulses supplied to the grid of tube ET3 is illustrated. As with the leading 18 degree phase shift of waveform D previously discussed, such 90 degree phase shift is an exaggeration employed for purposes of convenience of illustration, and is intended to indicate the phase shift occurring when storage track IT is empty and the track circuit apparatus is out of adjustment. As with the said leading phase shift such change in adjustment of the track circuit normally causes only a few degrees of improper phase shift. It will be seen from waveform I, however, that a phase shift such as illustrated by waveform I results in the same input pulses to integrator INT as those occasioned by waveform H, waveform H being the proper waveform when track section IT is empty and the track circuit apparatus is in correct adjustment. Such limiting of the width of the input pulses to integrator INT is provided by the 72 degree phase shifted reference current illustrated by waveform C. Thus the 72 degree phase shifter PS2, and associated clipper circuit CL2 and electron tube ET2, are employed to confine the width of the pulses supplied to integrator INT to a 72 degree width.

Referring again to FIG. 1, as described above, integrator INT is supplied at different times with a different series of pulses of direct current, the width of the direct current pulses of any one series being identical, but the width of the pulses of different series varying in accordance with the number of cars in storage track 1T, that is, the greater the available car space in storage track 1T the greater the width of the pulses representing such car space. Integrator INT integrates the pulses supplied thereto and provides at the output thereof a value of voltage or voltage signal proportional to the width of each pulse of the series of pulses supplied thereto during any period of time, that is, during a period of time when the car space available in storage track 1T remains constant, regardless of the brevity of such period of time. Such integrators or integrating circuits are well known in the art and no detailed discussion of the operation thereof is believed necessary.

The output from integrator INT is supplied over a back contact a of a slow acting motion detector relay, desig nated MDR and to be discussed, to a car space voltage meter designated CSM. This meter is preferably graduated to indicate or display the available car space in storage track 1T, such indication changing in accordance with the value of the voltage signal supplied thereto from integrator INT. That is, the greater the value of the voltage signal supplied to rneter CSM, the greater the available car space indicated by the meter. However, it is obvious that the meter could be graduated to display the number of cars in storage track 1T and in such case the smaller the value of the voltage signal supplied from integrator INT to the meter the greater the nurnber of cars in said track. The meter could, of course, have a standard voltage display dial and in such caseit would Having thus far described the track fullness apparatus 7 of my invention, I will now describe the apparatus for 7 detecting motion, that is, railway car movement in storage track 1T.

The principle employed in the car movement detection apparatus of my invention is that the phase angle of the alternating current supplied to track section IT is erratically changing when a railway car is moving over the track section or when each of a series of closely following cars enters the track section. Such erratic phase shifting is due to the intermittent track shunt caused by dirt or grease spots on the rails, or rust etc. on the wheels of the moving car. I utilize the reference voltage supplied from autotransformer TF1 to clipper circuit GL1 (FIG. 1) to provide a further reference signal and employ such reference signal to determine whether the output, from the secondary winding of transformer TF2 and supplied to clipper circuit CL3 (FIG. 1), is erratically shifting in phase.

Referring to FIGS. 1 and 1a it will be seen that the output pulses from clipper circuit CLl, as well as being supplied to the 180 degree phase shifter PS1, are also supplied to a triangular wave generator designated TWG. Similarly, the output pulses from clipper circuit CL3, as well as being supplied to the grid of electron tube ET3, 'are also supplied to a diiferentiator designated DIF. The output pulses from clipper circuit CL3 are also supplied to a delay circuit DLS to be discussed hereinafter.

The output from triangular wave generator TWG has a triangular wave shape indicated by the waveform diagram shown adjacent the block representing generator TWG, as indicated by the arrow extending from such iagram and pointing to the output circuit from the gener-ator. Similarly, the output from differentiator DIF has a peaked wave shape indicated by the waveform diagram above the block representing diiferentiator DIF, as indicated by the arrow extending from such diagram and pointing to the output circuit from the diiferentiator. It will be readily apparent from a brief glance at the waveform diagrams thus illustrated in FIG. la that, so long as the pulses supplied to theinput of diiferentiator DIF are in phase with the reference pulses supplied to generator TWG, or so long as each of the pulses supplied to the ditferentiator has the same phase displacement in relation to the phase of the pulse supplied to generator TWG, each of the downward spikes or pips of the peaked wave pulses from DIF, such downward spikes occurring at the time each of such pulses is in the lower half of its cycle, will coincide with an identical section of the slope of the respective triangular wave pulse from TWG which occurs during the same period of time. However, if one of more of a succession of pulses supplied to dilferentiator DIF have different phase displacements, in relation to the phase of the pulses supplied to generator TWG, the corresponding downward spikes at the output of DIF will not coincide with identical sections of the slopes of their associated triangular wave pulses. This lack of coincidence is employed to detect motion or railway car movement in storage track 1T since such lack of coincidence indicates continuous phase shifting of the alternating current supplied to the storage track, such phase shifting resulting from varying railway car shun-ts at varying points within the storage track. 7

As discussed in more detail later, the outputs from triangular wave generator TWG and differentiator DIF (FIG. 1a) are supplied to a diode bridge switching circuit labeled a difference sample generator and designated DSGl. The components of the generator are old and well known and only a brief discussion of such components, the cjrcuitryof the generator, and its. operation is believed necessary.

Generator DSGl'comprises a diode bridge circuit de-' signated DB, a transformer T having the usual primary and secondary windings, first and second capacitors C1 and C2, and first and second resistors R1 and R2. Capacitor C1 and resistor R1 are connected in multiple with each other and in series with the secondary winding of transformer T across first and second opposite terminals of the diode bridge DB. One of the remaining opposite terminals of the diode bridge circuit is connected in a series circuit through capacitor C2 and resistor R2 to ground. The output circuit of generator DSGI is conneoted to the juncture of capacitor C2 and resistor R2. A first input to generator D361 is supplied from .the output of triangular wave generator TWG to the fourth terminal of diode bridge DB. A second input to the generator is supplied from the output of differentiator DIF to one side of the primary winding of transformer T, the other side of such primary winding being connected to ground. It should be pointed out that the windings of transformer T are so arranged that a positive pulse from right to left (referring to FIG. 1a of the drawings) through the primary winding of transformer T will induce a positive pulse in the same direction through the secondary winding of the transformer. Therefore, as previously mentioned, the downward spikes of the output pulses from diiferentiator DIF are employed to actuate the switching circuit or generator DSGI, as discussed below. It will be readily apparent that the upward spikes of the output pulses from diiferentiator DIF could as well have been employed for actuation of generator DSGl and in such case transformer T would have its windings correspondingly arranged.

The output from generator DSGl is supplied to a gain circuit or amplifier AMPI, to be discussed later in this description. Generator DSGS operates in the following described manner.

Some time during the period that a triangular wave pulse is supplied from the output of generator TWG to the first input of generator DSGI and consequently to the diode bridge DB of the generator, a downward spike of a peaked pulse from the output of differentiator DIF is supplied to the second input of generator D561 and consequently to the primary winding of transformer T. Such spike of the peaked pulse occurs coincidental with some point on the slope of the triangular wave pulse and induces a pulse in the secondary winding of transformer T which causes the diodes of the diode bridge to conduct heavily. Consequently the voltage charge supplied to capacitor C2 at such time is proportionate to the point on the slope of the triangular wave pulse with which the downward spike of the peaked pulse coincided. When the downward spike of the peaked pulse terminates, the charge on capacitor C2 reverse biases enough of the diodes of diode bridge DB to prevent any conduction path through the bridge and accordingly, such charge remains on capacitor C2. As previously discussed, so long as there is no motion or car movement in storage track 1T the spikes of successive peaked pulses will coincide with the same points on the slopes of successive triangular wave pulses, and the voltage charge on capacitor C2 will remain constant once the capacitor is charged proportionately to the points on said slopes with which said spikes coincide.

When a railway car or cars are entering or moving through storage track 1T, the changing shunt across the rails or the intermittent shunting of the rails occasioned by the moving car or cars will cause changes in phase of the alternating track circuit current and, consequently,

the peaked pulses from diiferentia tor DIF will coincide with varying points on the slopes of their associated triangular wave pulsesfrom generator TWG. Such varying coincidence will cause pulses of current in one direction or another through resistor R2 of generator DSGI. For example, if the downward spike of one peaked pulse coincides witha point on the slope of its associated triangular wave and the downward spike of a following peaked pulse coincides with a point further down on the slope of its associated triangular wave, the voltage pulse supplied to capacitor C2 will be of a lower voltage than that previously supplied thereto and a pulse of current 1 will flow through resistor R2 towards capacitor C2. If,

however, the downward spike of said following peaked pulse coincides with a point further up on the slope of its associated triangular wave pulse than did the spike of the previous peaked pulse, the voltage pulse supplied to capacitor C2 will be of a higher voltage than that previously supplied thereto and a pulse will flow from capacitor C2 through resistor R2 due to the additional charge supplied to capacitor C2. Such charge will remain on capacitor C2 until another following peaked signal representing another phase angle displacement occurs. It is thus apparent that car movement in storage track 1T will cause an output from generator DSGl.

The output pulse from generator DSGl is supplied to a first amplifier designated AMP1 and thence to a clamp circuit designated CLMI. The output of CLMI rises to the peak height of the amplified pulse from amplifier AMP1 and remains there until a reset pulse, to be discussed hereinafter, is supplied to clamp circuit CLMl. The output from the clamp circuit CLMl is supplied as an input to a second diode bridge switching circuit or difference sample generator designated DSG2. Such generator is identical in construction and operation to generator DSGI previously discussed and, therefore, no detailed description thereof is considered necessary. It is believed expedient to point out at this time that a third difference sample generator, designated D583 and to be discussed later, is also employed and that this generator is also identical in construction and operation to generator DSGl.

In order to provide a peaked or sampling pulse for switching or gating generators DSG2 and DSG3, the output from differentiator DIF is supplied to first and second delay circuits designated DLl and DLZ, respectively. Delay circuit DLl delays the original peaked or sampling pulse from DIF for a long enough period to insure that the output from clamp circuit CLMI and supplied to generator DSGZ has leveled off. Delay circuit DLZ performs a similar function, as discussed hereinafter.

The output pulse from generator DSGZ is supplied to a second amplifier AMPZ and thence to a second clamp circuit CLMZ whose output rises to the peaked height of the amplified pulse and remains there until a reset pulse, as discussed hereinafter, is supplied to clamp circuit CLMZ. The output from clamp circuit CLMZ is supplied to the third difference sample generator DSGSe. As previously mentioned delay circuit DLZ delays the original peaked or sampling pulse from differentiator DlF for a sufiicient period to insure that the output from clamp circuit CLM2 supplied to generator DSGS has leveled off. Amplifiers AMP1 and AMPZ, clamp circuits CLMl and CLM2, and generators DSG2 and D863 provide amplification, in response to the original car movement signals from generator DSGl, so that usable output signal pulses are provided at the output of generator DSG3.

that the resulting pulse from DL3 occurs well after the delayed peakedpulse supplied from delay circuit DLZ to DSGZ. Each such delayed pulse from the output of delay circuit DL3 is supplied .as an input to clamp circuits CLMl and CLMZ and resets the clamp circuits sothat they can function again on the next pulse supplied thereto from amplifiersAMPl and AMPZ, respectively.

The output from generator DSG3 is supplied as an ini put to a full wave rectifier designated RT, the output from such rectifier being supplied as an input to a one-shot or monostable multivibrator designated MV and provided with a threshold adjustment designated TA. Multivibrator MV i'semployed as a pulse stretcher to to stretch out signal pulses from rectifier RT s'uificiently to energize the previously mentioned motion detector relay MDR, since the signal pulses from rectifier RT representing car movement in storage track 1T have a very short duration. Such pulses must have a magnitude above the level provided by the threshold adjustment TA in order to trigger multivibrator MV to produce an output for energizing relay MDR. The control winding of relay MDR is connected between the output of multivibrator MV and ground.

As previously mentioned relay MDR is a slow acting relay, that is, slow to become picked up when energy is first supplied thereto and slow to release once it becomes picked up and energy is removed therefrom. Such slow acting features of the relay are indicated by the double headed arrow drawn through the movable portion of contact a of the relay shown in FIG. 1 of the drawings. The slow pickup feature of the relay is to prevent its becoming picked up when only a few pulses of energy are supplied thereto from multivibrator MV, as for example, when the apparatus is first turned on at the beginning of a period of yard operations. The slow release feature of the relay is to enable the relay to bridge the off periods of the signal pulses from MV once it has become picked up in response to such pulses, that is, to enable the relay to remain picked up in response to said pulses once it has become picked up.

By the above description it is readily apparent that the apparatus of my invention as shown in FIG. 1 operates to determine the track fullness or distance to travel to coupling in storage track 1T, such track fullness or distance to travel being represented by a proportional output signal from integrator INT. As shown in FIG. 1 the output signal from integrator INT is employed to operate a meter which will display an indication indicative of the track fullness or distance to travel, providing no motion or car movement is detected in the storage track by the apparatus of my invention shown inFIG. 1a. 1 If such car movement is detected relay MDR becomes pickedup and opens its back contact a which interrupts the output from integrator INT to meter CSM and causes the meter to display a track full or no space available indication since no valid indication can be given at that time. When car movement in storage track IT has ceased, relay MDR will release following the expiration of its slow release period and a valid track fullness or distance to travel determination can again be made and the proper indication displayed. It will be understood that the output signal provided over back contact a of relay MDR can be employed to operate track fullness or distance to travel devices other than a meter or display device, that is, a device such as a computer, and my invention is not intended to be confined to the use of a display device as shown.

With the exception of the difference sample generators or diode bridge switching circuits D861, D862 and D863, which were discussed in detail above, the circuits represented by the blocks in FIGS. 1 and 1a are well known and may all be found described or shown,'for example, in the text Pulse and Digital Circuits by Millman and T aub and published by the McGraw-Hill Book Company, Inc. in .1956. The manner of interconnecting such circuits and apparatus will, in thelight of the above description, be well within the skill of the technician in the art.

From this description it is apparent that, with the apparatus of my invention as shown in FIGS.'1 and la of the drawings, a track fullness or distance to travel to coupling system is provided which employs the phase or interrupting such signal if railway, car movement is detected in said storage track.

" Although I have herein shown and described only one form of apparatus embodying my invention,it is underi ll stood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention what I claim is:

1. Apparatus for deriving a track fullness signal distinctly representing the distance from a first point in a railway track section to a shunt across the rails of the track section, said apparatus comprising, in combination,

(a) an alternating current signal supplied to the rails of said track section at said first point so that the phase angle of such signal shifts in accordance with the impedance of the track section between such point and said shunt,

(b) and means responsive to the shift of the phase angle of said alternating current signal for producing said track fullness signal.

2. Apparatus for deriving a signal distinctly representing the distance from a first point in a railway track section to a shunt across the rails of the track section, said apparatus comprising, in combination,

(a) a first alternating current signal,

(b) a second alternating current signal having a known basic phase relationship with said first signal and connected with said track section at said first point so that such second signal is phase shifted in accordance with the impedance of .said track section between said first point and said shunt,

(c) and means responsive to said first signal and said shifted second signal for deriving said distance representing signal in accordance with said phase shift.

3. Apparatus for deriving a track fullness signal distinctly representing the distance from a first point in a railway track section to a shunt across the rails of the track section, said apparatus comprising, in combination,

(a) a first alternating current signal of constant frequency,

(b) a second alternating current signal of said frequency and having a known basic phase relationship With said first signal and connected with said track section at said first point so that the second signal is phase shifted in accordance with the impedance of said track section between said first point and said shunt,

(c) means for changing said first signal and said shifted second signal into square wave signals,

(d) and a NOR circuit having said square wave signals as its inputs and deriving as its output said track fullness signal.

4. Apparatus for determining the distance from the entrance end of a storage track in a railway car classification yard to the nearest railway car in such track, said apparatus comprising, a

(a) a source of alternating current of constant frequency,

(b) first transformer means coupling a first value of alternating current from said source across the rails of'said track at said entrance end,

(c) second transformer means coupled to said first transformer means and said source so as to derive a second value of alternating current which is displaced in phase in accordance with the impedance presented to said first value of alternating current by V the section of said storage track between the entrance 'end thereof and the trackshunt occasioned by the nearest pair of wheels and associated axle of said rail- (g) means connected to said second value of alternating current for changing the wave thereof to a square wave of the same frequency,

(11) a NOR circuit,

(i) conductors for supplying said square waves to the input of said NOR circuit,

(j) and integrating means connected to the output of said NOR circuit for deriving a direct current signal representing said distance from the entrance end of the storage track to the nearest railway car in such track.

5. Apparatus for producing a signal representive of the available car space in a storage track in a railway car classification yard, said apparatus comprising, in combination,

(a) a source of alternating current,

(b) means responsive to said current for producing a first square wave signal in phase with said current,

(0) phase shifting means for shifting said square wave signal to its directly opposite phase,

(:1) means for supplying an alternating current from said source across the rails of said storage track at a first point in such track whereby such alternating current is phase shifted in accordance with the impedance of said rails between said first point and a shunt across the rails of the storage track,

(2) means responsive to said phase shifted alternating current for producing a second square wave signal in phase with such phase shifted alternating current,

(1) a NOR circuit organization having at least first and second input circuits and an output circuit,

(g) means for supplying said first and second square waves to said first and second input circuits, respectively,

(h) and an integrator connected to said output circuit for producing said signal representative of available car space in said storage track.

6. Apparatus in accordance with claim 5 and further characterized by (a) motion detection means, responsive to erratic phase shifts in the alternating current supplied across the rails of said storage track, for producing a signal representative of railway car movement in such track,

(12) and means, responsive to the car movement signal,

for interrupting the signal produced by said integrator.

7. A track fullness system for a storage track in a railway car classification yard, said system comprising, in

combination,

(a) means for supplying a first alternating current across the rails of said storage track, such alternating current being shifted in phase by and in proportion to the impedanceof the rails between the point of supply across such rails and the nearest shunt across 8. Apparatus in accordance with claim 7 and further characterized by (a) means responsive to erratic phase shifts in' said first alternating current, caused by the movement of a railway car over the rails ofsaid storage track, for producinga signal representing car movement,

(b) and means responsivevto said car movement signal for interrupting said available car space signal.

9. Apparatus for detecting railway car movement in a storage track in a railway car classification yard, said apparatus comprising, in combination,

(a) means responsive to a reference alternating current for producing a succession of triangular wave pulses in accordance with the frequency of said alternating current,

(b) means, responsive to an alternating current having the same frequency as said reference current and supplied across the rails of said storage track, for producing a succession of peaked wave pulses in accordance with the frequency of said alternating current, each successive peaked pulse being associated With a correspondingly successive one of the triangular pulses, and all of such peaked pulses oc curring at the same point in time in the duration of their respectively associated triangular wave pulses when there is no railway car movement in said storage track and some of such peaked pulses being shifted to difierent points in time in the duration of their respectively associated triangular wave pulses when there is railway car movement in said storage track,

(c) a diode bridge switching device responsive to said triangular wave pulses and said peaked wave pulses for producing car movement signal pulses when some of said peaked wave pulses are shifted in time,

(d) amplifying mean responsive to said car movement signal pulses for producing amplified car movement signal pulses,

(e) a full wave rectifier responsive to said amplified car movement signal pulses for producing direct current car movement signal pulses,

(f) a monostable multivibrator responsive to said direct current car movement signal pulses for producing direct current output pulses of a longer duration,

(g) a motion detector relay connected to the output of said multivibrator and becoming picked up in response to a series of the output pulses from the multivibrator,

(h) and circuit means controlled by a contact of said relay.

10. A system for determining the available car space in a storage track in a railway car classification yard, said storage track having a first alternating current connected across the rails thereof adjacent the entrance end of the track and a shunt across said rails at some point within the track, said system comprising, in combination,

(a) means responsive to said first alternating current for producing a second alternating current shifted in phase proportionately to the impedance presented to the first alternating current by the rails of said storage track between said entrance end thereof and said shunt across the rails,

(b) means responsive to said second alternating current for producing square wave pulses in phase with such second current,

(c) a third alternating current in phase with said first alternating current,

(d) means responsive to said third alternating current for producing second square wave pulses opposite in phase to said third current,

(6) means responsive to said third alternating current for producing third square wave pulses having a phase shift lagging such third current by an angle equal to the maximum possible phase shift in said first alternating current due to said storage track rail impedance,

(1) and an electron tube NOR circuit having said first, second and third square wave pulses as its separate inputs and producing as its output fourth square wave pulses each having a Width proportionate to the car space available in said storage track.

11. Apparatus in accordance with claim 10 and further characterized by (a) an integrator responsive to said fourth square wave pulses for producing an integrated direct current proportional to the width of each of a series of such fourth pulses, the magnitude of such direct current representing the space available in said storage track.

12. Apparatus in accordance with claim 11 and further characterized by (a) means responsive to said second alternating current for producing a succession of peaked wave pulses,

(b) means responsive to said third alternating current for producing a succession of triangular wave pulses, each pulse of such succession being associated with a corresponding successive one of said peaked wave pulses,

(c) diode bridge switching means, responsive to said peaked and triangular Wave pulses, for producing output pulses when successive ones of said peaked pulses coincide with different points on the slopes of their corresponding triangular wave pulses,

(d) amplifying means for amplifying said output pulses,

(e) rectifying means for rectifying said amplified pulses,

(1) pulse stretching means, responsive to said rectified pulses, for producing second output pulses of a longer duration than said rectified pulses,

(g) a relay having its control winding so connected as to be energized by said second output pulses, (h) and means, controlled by said relay when energized, for interrupting the direct current produced by said integrator, the energization of such relay indi cating railway car movement in said storage track.

References Cited in the file of this patent UNITED STATES PATENTS 3,019,390 MacMillan Jan. 30, 1962 3,021,481 Kalmus et a1 Feb. 13, 1962 3,056,022 Phelps Sept. 25, 1962 3,075,086 Mussard Jan. 22, 1963 3,077,544 Connelly Feb. 12, 1963 3,100,098 Crawford Aug. 6, 1963 

1. APPARATUS FOR DERIVING A TRACK FULLNESS SIGNAL DISTINCTLY REPRESENTING THE DISTANCE FROM A FIRST POINT IN A RAILWAY TRACK SECTION TO A SHUNT ACROSS THE RAILS OF THE TRACK SECTION, SAID APPARATUS COMPRISING, IN COMBINATION, (A) AN ALTERNATING CURRENT SIGNAL SUPPLIED TO THE RAILS OF SAID TRACK SECTION AT SAID FIRST POINT SO THAT THE PHASE ANGLE OF SUCH SIGNAL SHIFTS IN ACCORDANCE WITH THE IMPEDANCE OF THE TRACK SECTION BETWEEN SUCH POINT AND SAID SHUNT, (B) AND MEANS RESPONSIVE TO THE SHIFT OF THE PHASE ANGLE OF SAID ALTERNATING CURRENT SIGNAL FOR PRODUCING SAID TRACK FULLNESS SIGNAL. 